The present invention relates to a method and apparatus for determining the recording pulse parameters of an optical disc by reading standard recording pulse parameters from a writable optical disc, the optical disc having standard recording pulse parameters prerecorded to a specific area thereof, setting the recording pulse parameters of a recording and reproducing device, and recording or reproducing data from the disc.
The DVD-RAM specification describes one example of a high data capacity rewritable optical disc, and devices capable of writing 2.6 gigabytes of data using a mark edge recording method to one side of a 12 cm diameter disc using a phase change recording film are available. Looking to achieve an even higher density optical disc medium; the present inventors have been studying a disc recording method (cf., JP2679596) capable of reducing shifting in the mark edge position as a result of heat interference between marks, a problem with high density recording in phase change optical disc media.
When this disc recording method records data to disc as amorphous marks using a mark edge recording technique, recording is accomplished using a laser beam of plural pulse streams, known as a multipulse beam. Because the size of the recorded marks and the distance of the space between marks is so small in high density recording, the heat of the laser light applied to form a particular mark is also transferred to the marks therebefore and thereafter, causing distortion in the shape of the particular mark and the marks therebefore and thereafter. To prevent this, marks are recorded by precompensating for heat interference between marks by changing the position of the first pulse in the multipulse stream used for pulse formation according to the relationship between the length of a particular mark and the length of the preceding space, and changing the position of the last pulse in the multipulse stream used for pulse formation according to the relationship between the length of the particular mark and the length of the following space. This control of recording pulse position is typically referred to as recording compensation. There are values in the recording pulse parameters (recording compensation parameters) that differ in specific mark and space combinations, resulting in tables such as shown in FIG. 2. The relationship between mark and space positions resulting from the values shown in the tables is shown in FIG. 3.
The recording pulse parameters for accomplishing recording compensation must be prestored to the optical disc or the disc recorder in order to achieve an actual optical disc recording and reproducing apparatus. Plural discs with different characteristics, that is, with different recording pulse parameters, can be used by recording these values to the disc so that the recording device can read the values when the disc is used.
Due to environmental changes and variations in the characteristics of components used in mass-produced optical disc recording and reproducing devices, the individual devices will not necessarily have identical characteristics. Considering, for example, a head having the laser and a laser driving means used for recording, the pulse width will change due primarily to variation in the laser characteristics even if the same current waveform is supplied to the laser. Individual devices will also not necessarily produce the same emission waveform. A certain amount of variation also occurs in the characteristics of mass produced optical discs, and the same mark shape will not necessarily be achieved with each individual disc even if recorded with identical emission waveforms.
Therefore, a problem has been that if standard recording pulse parameters determined by a reference device having standard characteristics using a reference disc having standard characteristics are used as is with mass-produced discs and devices having characteristics that deviate from the standard characteristics, recording and reproduction will not be possible depending upon the particular combination, and quality defects occur.
Moreover, while the problem is small if the discs are manufactured under sufficient quality control and deviation from the standard characteristics is minimal, if the standard recording pulse parameters prerecorded to the disc differ greatly from actual disc performance, it will not be possible to achieve full performance from the disc even if the standard recording pulse parameters read by the device from the disc are faithfully reproduced.
The present invention solves the aforementioned problems and has as a first object to provide, in an optical disc recording parameter determining method that reads the above-noted standard recording pulse parameters from a writable optical disc having standard recording pulse parameters prerecorded to a specific area thereof, sets the recording pulse parameters of a recording and reproducing apparatus, and records and reproduces data, an optical disc recording parameter determining method whereby the effects of variation in the characteristics of a writable optical disc and recording and reproducing apparatus can be reduced.
Furthermore, a second object is to provide an optical disc recording parameter determining method whereby good recording characteristics can be achieved even when there is a difference between the optical disc characteristics and standard recording pulse parameters of a writable optical disc having standard recording pulse parameters prerecorded to a specific area thereof.
Furthermore, a third object is to provide an optical disc recording parameter determining method capable of reducing the number of read/write operations and shortening the required time compared with the optical disc recording parameter determining method achieving the above-noted second object.
To achieve the above-noted first object, in an optical disc recording parameter determining method for reading standard recording pulse parameters from a writable optical disc to which standard recording pulse parameters are prerecorded to a specific area, setting the recording pulse parameters of a recording and reproducing device, and recording and reproducing data: all plural leading mark-edge pulse parameters, which are determined according to a particular mark length and preceding space length combination, and all trailing mark-edge pulse parameters, which are determined according to a particular mark length and following space length combination, in the standard recording pulse parameters are uniformly shifted a specific time; and a value corrected from the standard parameters so that the read/write signal jitter is less than or equal to an allowed value is set as a recording pulse parameter of the recording and reproducing device for reading and writing data.
Furthermore, to achieve the above-noted second object, recording patterns are recorded corresponding to each of plural leading mark-edge pulse parameters defined by a preceding space length and particular mark length combination, and each of plural trailing mark-edge pulse parameters defined by a particular mark length and following space length combination in the standard recording pulse parameters; and the values individually correcting the standard parameters so that the read signal jitter is less than or equal to an allowed value are set as the recording pulse parameters of the recording and reproducing device and used for data reading and writing.
Furthermore, to achieve the above-noted third object, recording patterns are recorded for each of the plural leading mark-edge pulse parameters selected from among the standard recording pulse parameters and determined by a preceding space length and particular mark length combination, and each of the plural trailing mark-edge pulse parameters selected from among the standard recording pulse parameters and determined by a particular mark length and following space length combination, and the values individually correcting the standard parameters so that read signal jitter is less than or equal to an allowed value are set as the recording pulse parameters of the recording and reproducing device. For recording pulse parameters not selected, values interpolated from the correction values of the selected recording pulse parameters are set as the recording pulse parameters of the recording and reproducing device and used for data reading and writing.
A first aspect of the present invention is a method for obtaining a recording pulse parameter that is a method for reading standard recording pulse parameters from a writable optical disc to which are prerecorded standard recording pulse parameters defining recording pulse position information for each of plural possible mark length and space length combinations, correcting a standard recording pulse parameter, and obtaining a best recording pulse parameter, said method:
performing a first test write to the optical disc using position information for all mark length and space length combinations in the standard recording pulse parameters;
reproducing the first test write and detecting a first jitter from the reproduced signal;
adding a first specific amount of change uniformly to the position information for all mark length and space length combinations in the standard recording pulse parameters, and performing a second test write to the optical disc using the uniformly changed position information;
reproducing the second test write and detecting a second jitter from the reproduced signal; and
comparing the first jitter and second jitter, and selecting the position information used for the test write with less jitter.
A second aspect of the present invention is the method of the first aspect of the invention for obtaining a recording pulse parameter, this method further:
adding a second specific amount of change uniformly to the position information for all mark length and space length combinations in the standard recording pulse parameters, and performing a third test write to the optical disc using the uniformly changed position information;
reproducing the third test write and detecting a third jitter from the reproduced signal; and
comparing the first jitter, second jitter, and third jitter, and selecting the position information used for the test write with least jitter.
A third aspect of the present invention is a method for obtaining a recording pulse parameter that is a method for reading standard recording pulse parameters from a writable optical disc to which are prerecorded standard recording pulse parameters defining recording pulse position information for each of plural possible mark length and space length combinations, correcting a standard recording pulse parameter, and obtaining a best recording pulse parameter, said method:
performing a first test write to the optical disc using position information for any one combination selected from all mark length and space length combinations in the standard recording pulse parameters;
reproducing the first test write and detecting a first jitter from the reproduced signal;
adding a first specific amount of change to the position information for the above one combination selected from all mark length and space length combinations in the standard recording pulse parameters, and performing a second test write to the optical disc using the changed position information;
reproducing the second test write and detecting a second jitter from the reproduced signal; and
comparing the first jitter and second jitter, and selecting the position information used for the test write with less jitter.
A fourth aspect of the present invention is the method of the third aspect for obtaining a recording pulse parameter, said method further:
adding a second specific amount of change to the position information for the above one combination selected from all mark length and space length combinations in the standard recording pulse parameters, and performing a third test write to the optical disc using the changed position information;
reproducing the third test write and detecting a third jitter from the reproduced signal; and
comparing the first jitter, second jitter, and third jitter, and selecting the position information used for the test write with least jitter.
A fifth aspect of the present invention is the method of the third aspect for obtaining a recording pulse parameter wherein when there is first position information selected for any one combination, and second position information selected for a separate combination, position information intermediately between the two combinations is obtained by interpolation from the first position information and the second position information.
A sixth aspect of the present invention is an apparatus for obtaining a recording pulse parameter that is an apparatus for reading standard recording pulse parameters from a writable optical disc to which are prerecorded standard recording pulse parameters defining recording pulse position information for each of plural possible mark length and space length combinations, correcting a standard recording pulse parameter, and obtaining a best recording pulse parameter, said apparatus comprising:
a test writing means for performing a first test write to the optical disc using position information for all mark length and space length combinations in the standard recording pulse parameters,
a jitter detection means for reproducing the first test write and detecting a first jitter from the reproduced signal,
the test writing means adding a first specific amount of change uniformly to the position information for all mark length and space length combinations in the standard recording pulse parameters, and performing a second test write to the optical disc using the uniformly changed position information, and
the jitter detection means reproducing the second test write and detecting a second jitter from the reproduced signal,
and further comprising a selection means for comparing the first jitter and second jitter, and selecting the position information used for the test write with less jitter.
A seventh aspect of the present invention is the apparatus of the sixth aspect for obtaining a recording pulse parameter, wherein:
the test writing means further adds a second specific amount of change uniformly to the position information for all mark length and space length combinations in the standard recording pulse parameters, and performs a third test write to the optical disc using the uniformly changed position information;
the jitter detection means reproduces the third test write and detects a third jitter from the reproduced signal; and
the selection means compares the first jitter, second jitter, and third jitter, and selects the position information used for the test write with least jitter.
An eighth aspect of the present invention is an apparatus for obtaining a recording pulse parameter that is an apparatus for reading standard recording pulse parameters from a writable optical disc to which are prerecorded standard recording pulse parameters defining recording pulse position information for each of plural possible mark length and space length combinations, correcting a standard recording pulse parameter, and obtaining a best recording pulse parameter, said apparatus comprising:
a test writing means for performing a first test write to the optical disc using position information for any one combination selected from all mark length and space length combinations in the standard recording pulse parameters, and
a jitter detection means for reproducing the first test write and detecting a first jitter from the reproduced signal,
the test writing means adding a first specific amount of change to the position information for the above one combination selected from all mark length and space length combinations in the standard recording pulse parameters, and performing a second test write to the optical disc using the changed position information, and
the jitter detection means reproducing the second test write and detecting a second jitter from the reproduced signal, and
further comprising a selection means for comparing the first jitter and second jitter, and selecting the position information used for the test write with less jitter.
A ninth aspect of the present invention is the apparatus of the eighth aspect for obtaining a recording pulse parameter, wherein:
the test writing means adds a second specific amount of change to the position information for the above one combination selected from all mark length and space length combinations in the standard recording pulse parameters, and performs a third test write to the optical disc using the changed position information;
the jitter detection means reproduces the third test write and detects a third jitter from the reproduced signal; and
the selection means compares the first jitter, second jitter, and third jitter, and selects the position information used for the test write with least jitter.
A tenth aspect of the present invention is the apparatus of the eighth aspect for obtaining a recording pulse parameter wherein when there is first position information selected for any one combination, and second position information selected for a separate combination, position information intermediately between the two combinations is obtained by interpolation from the first position information and the second position information.
As noted above, in an optical disc recording parameter determining method that reads standard recording pulse parameters from a writable optical disc having standard recording pulse parameters prerecorded to a specific area thereof, and sets the recording pulse parameters of the recording and reproducing device for reading and writing data, the optical disc recording parameter determining method according to the present invention can reduce the effects of variation in the characteristics of the writable optical disc and the recording and reproducing device. In addition, good recording characteristics can be achieved even if there is a difference between the optical disc characteristics and the standard recording pulse parameters of the optical disc to which standard recording pulse parameters are prerecorded to a specific area thereof. Therefore, the invention has the effect of improving yield in the mass production of optical discs and recording and reproducing devices, improving product quality, and reducing cost.